Abstract: Solar energy conversion and high-value chemical production are of utmost importance. However, the development of efficient photocatalysts with strong redox ability remains challenging. Here we report a unique 3D/0D In₂S₃/WO₃ S-scheme heterojunction photocatalyst obtained by depositing WO₃ quantum dots (QDs) onto hierarchical In₂S₃ microflowers. The In₂S₃/WO₃ composite exhibits outstanding visible light absorption, with a maximum optical response of up to 600 nm. The electronic interaction and charge separation at interfaces are explored by in situ X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations. The difference in work function causes In₂S₃ to donate electrons to WO₃ upon combination, leading to the formation of an internal electric field (IEF) at the interfaces. Due to the IEF and bent energy bands, the transfer and separation of photogenerated charge carriers follow an S-scheme pathway within In₂S₃/WO₃. Owing to the strong redox ability, spatial charge separation and lower H₂-generation barrier of S active sites, the optimized In₂S₃/WO₃ heterojunctions show enhanced photocatalytic hydrogen evolution of 0.39 mmol h^-1 g^-1, 6.7 times that of pristine In₂S₃. In addition, the In₂S₃/WO₃ S-scheme heterojunctions afford a remarkable activity for photocatalytic nitrobenzene hydrogenation with nearly 98% conversion and 99% selectivity of aniline within 1 h. Our work might present new insights into developing efficient S-scheme heterojunctions for various photocatalytic applications.

Key words: S-scheme heterojunctions, In₂S₃ microflowers, WO₃ quantum dots, H₂ production, Electron transfer